You have an empty 3-gallon jug, an empty 5-gallon jug, and an unlimited water source. What is the minimum number of steps (filling, pouring, or emptying) to measure out exactly 4 gallons into the 5-gallon jug?
6 steps
1) Fill 5-gal jug (5g:5, 3g:0). 2) Pour 5-gal into 3-gal (5g:2, 3g:3). 3) Empty 3-gal (5g:2, 3g:0). 4) Pour 2 gal from 5-gal into 3-gal (5g:0, 3g:2). 5) Fill 5-gal jug completely (5g:5, 3g:2). 6) Pour from 5-gal into 3-gal until full (adds 1 gal), leaving 4 gallons in the 5-gal jug.
About this riddle
Math riddles hide a calculation inside a short story. Pull out the numbers, work out what is being asked, and watch for a trick such as a unit change.
Difficulty: Hard. More like this: Math riddles with answers or try Target 24 for a different kind of puzzle.
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